ALT stands for Alanine Aminotransferase, which is an enzyme mainly found in the liver, but also in smaller amounts in other organs like the kidneys and muscles. ALT plays a key role in breaking down food into energy by catalyzing the transfer of an amino group from alanine to α-ketoglutarate, producing pyruvate and glutamate in the process. Clinically, the ALT blood test measures the level of this enzyme in your blood. Normally, ALT levels in the blood are low, but when liver cells are damaged, they release ALT into the bloodstream, causing elevated levels. Therefore, the ALT test is commonly used to assess liver health and detect liver damage or disease. It is often included in liver function or comprehensive metabolic panels. High ALT levels can indicate liver problems such as inflammation, fatty liver disease, hepatitis, liver cirrhosis, and damage from toxins or drugs. Doctors may order an ALT test if you have symptoms related to liver disease or if you're at risk due to factors such as alcohol use, obesity, diabetes, or exposure to hepatitis virus. In summary, ALT is a liver enzyme that serves as a biomarker for liver health, with the ALT blood test helping to diagnose and monitor liver conditions. If you want, I can provide more details on normal ranges, causes of abnormal levels, or how the test is performed. Just let me know.